The present invention refers to a pump motor unit comprising an electric driven motor, which is cooled by means of a liquid.
Different pump motor units for propulsion of a liquid through different devices are earlier known. These pump units vary in structure dependent on the liquid to be pumped and where the unit is mounted. Pump motor units of this type are used in a wide variety of applications and a particularly important one is in washing machines or the like used in the home, such as clothes and dishwashers. In these applications, a rinsing fluid is pumped through the machine and usually a centrifugal pump driven by an electric motor is used to effect the circulation of the rinsing liquid.
The present invention refers primarily to domestic machines and it is described in connection to such machines but it is in no way limited to this type of machine.
A common problem in, for instance dish washing machines is the small space available for the pump motor unit. This unit which has to pump the wash liquor through the machine and to rinse the dish is usually arranged at the lower side of the machine near the floor. The outer dimensions of the machine are generally determined by standardization specifications and an increase of the active volume of the machine may then only be made on account of the space for the pump motor unit. It is therefore a desire to make this unit as small as possible.
The electric motor of the pump motor unit of this type is generally cooled by jets of air caused by a cooling blower built into the motor. The part of the motor situated furthest away from the dish container is thereby generally exposed to efficient cooling, whereas the portion situated nearest to the dish container is poorly cooled due to the high temperature of the dish drum and the very small air space at that location. The problem can be reduced by provision of casings which deflect the air jets in suitable manner. During all conditions it is necessary to have such a rapid air flow as possible. This in turn can cause waste water on the floor below the motor to be drawn into the motor causing a short circuit. It is therefore a further desire to be able to eliminate the blower system for air cooling of the motor.